Embodiments of the invention relate generally to lighting apparatuses and related technologies. More particularly, embodiments of the invention relate to a light apparatus having an optical component with coating materials for imparting a color filtering effect to light sources.
LED lamps provide a variety of advantages over traditional incandescent and fluorescent lamps, including but not limited to a longer life expectancy, higher energy efficiency, and full brightness without requiring time to warm up. As known in the art, LEDs (which as used herein also encompasses organic LEDs, OLEDs and the like) are solid-state semiconductor devices that convert electrical energy into electromagnetic radiation which includes visible light (wavelengths of about 400 to 750 nm). An LED typically includes a chip (die) of a semiconducting material doped with impurities to create a p-n junction. The LED chip is electrically connected to an anode and cathode, all of which are often mounted within a package. In comparison to other lamps such as incandescent or fluorescent lamps, LEDs emit visible light is more directional in a narrower beam.
FIG. 1 is a perspective view of a conventional LED-based lighting apparatus 10 suitable for area lighting applications. The lighting apparatus (which may also be referred to as a “lighting unit” or “lamp”) 10 includes a transparent or translucent cover or enclosure 12, a threaded base connector 14, and a housing or base 16 between the enclosure 12 and the connector 14.
An LED-based light source (not shown) which is an LED array including multiple LED devices, is located at the lower end of the enclosure 12 and adjacent the base 16. Because LED devices emit visible light in narrow bands of wavelengths, for example, green, blue, red, etc., combinations of different LED devices are often combined in LED lamps to produce various light colors, including white light. Alternatively, light that appears substantially white may be generated by a combination of light from a blue LED and a phosphor (e.g., YAG:Ce) that converts at least some of the blue light of the blue LED to a different color; the combination of the converted light and the blue light can generate light that appears white or substantially white. The LED devices are mounted on a carrier mounted to or within the base 16, and the LED devices are encapsulated on the carrier with a protective cover which formed of an index-matching material to enhance the efficiency of visible light extraction from the LED devices.
To promote the capability of the lighting apparatus 10 to emit visible light in a nearly omnidirectional manner, the enclosure 12 shown in FIG. 1 is substantially spheroidal or ellipsoidal in shape. To further promote a near omnidirectional lighting capability, the enclosure 12 is formed of a material that enables the enclosure 12 to function as an optical diffuser. Materials employed to produce the diffuser include polyamides (e.g., nylon), polycarbonate (PC), or polypropylene (PP); or the like. These polymeric materials also include SiO2 to promote refraction of the light and thereby achieve a white reflective appearance. The inner surface of the enclosure 12 may be provided with a coating (not shown) that contains a phosphor composition.
FIG. 2 is a graph from a publication: “Controllable Energy Transfer in Fluorescence Upconversion of NdF3 and NaNdF4 Nanocrystals”, Li et al., Optics Express, Vol. 18 Issue 4, pp. 3364-3369 (2010). The graph shows optical properties for NdF3 and NaNdF4 nanocrystals dispersed in water at the same molar concentration of 180 mM. FIG. 2 shows absorption spectra observed for the NdF3 and NaNdF4 nanocrystals. Absorption peaks of NdF3 and NaNdF4 were 578 and 583 nm, respectively, and therefore well within the yellow light wavelength range (about 560 to about 600 nm (nanometer)).
Though the use of combinations of different LED devices and/or phosphors can be utilized to promote the ability of LED lamps to produce a white light effect, other approaches are desirable as alternatives or in addition thereto.